Fig. 7. Spearman correlations of major solutes with SiO₂ concentrations for six sampling stations along the main stem of the Piracicaba River. Numbers are ranked from upriver to downriver sampling sites to show possible trends in river chemistry. The designation of "Cat" refers to the mean correlation value for Na⁺, Ca²⁺, and Mg²⁺, whereas "An" refers to the mean correlation value for Cl^- and SO^2-₄. SS is suspended sediments. Numbers 1, 3, and 5 are upstream sites, and 7, 8, and 10 are downstream sites.